If that same price drop is sustained in regular trading Thursday, it will cost Spiegel more than $1.3 billion in the space of less than 24 hours. Spiegel's co-founder Bobby Murphy will take a haircut of $1.1 billion.

At the time of the IPO, both men owned 210.97 million shares, including 97.16 million of Class A shares, 5.86 million of Class B and 107.94 million of Class C. Spiegel was granted an additional 37.4 million shares upon conclusion of the IPO.

Given the size of their stakes, any $5 drop in Snap's stock price will slash the value of their holdings by over $1 billion.

Still, even if the shares drop to $17, their holdings will be worth more than $3.5 billion each.

The company's earliest venture capital investors, Benchmark Capital and Lightspeed Venture Partners, are also in line for a big haircut when markets open on Thursday.

A $5 drop in Snap will cost Benchmark $604 million and Lightspeed $410 million, based on their post-IPO stakes.